In certain vital systems, such as, in automatic vehicle speed control systems for railroad and mass and/or rapid transit operations, it is essential to accurately sense the actual speed of the moving train or vehicles. It is common practice in measuring the velocity or speed of trains and transit vehicles to employ a generating device which is suitably associated with the rotation of the bull or drive gear which is directly connected to the axle of a vehicle for producing discrete signals in response to the movement thereof. While it is apparent that the signal generating device may take the form of any suitable type, it has been found that the electromagnetic type of signal generator is prevalent in the industry. In practice, the electromagnetic pickup device includes a permanent magnet and coil arrangement which is influenced by the teeth of the ferromagnetic gear or toothed wheel. The magnetic core of the pickup coil includes a pole piece which is spaced a given distance from the face of the teeth of the gear. The toothed gear is mounted directly onto the axle of the vehicle so that vehicular movement causes rotation of the wheels which, in turn, moves the gear teeth in relation to the inductive pickup coil. It will be appreciated that rotational movement of the gear-toothed gear causes alternating current voltage signals to be induced in the pickup coil. Further, it will be appreciated that the frequency of the alternating current signals is proportional to the angular rotation of the tooth wheel which, in turn, is proportional to the speed of the moving vehicle. It is readily obvious that when the train or vehicle is not moving or stationary, the rotation of the toothed gear should also cease so that no alternating current signals will be developed in the inductive pickup coil. Thus, the alternating current voltage signals induced in the pickup coil may be interpreted as an input signal which is only present when the vehicle is moving along its route of travel. Thus, it is common practice to employ the absence of the alternating current signals as an indication that the train is stopped at a station so that the doors may be safely opened to permit the egress and ingress of the passengers. Thus, it is necessary to provide that the electromagnetic speed sensing device is both electrically stable and mechanically sound in order to meet the criteria of fail-safe operation.